Axial piston hydraulic unit



y 4, 1968 c. J. GANTZER 3,332,793

AXIAL PISTON HYDRAULIC UNIT Filed Aug. 9, 1965 United States Patent 3,382,793 AXIAL PISTON HYDRAULIC UNIT Charles J. Gantzer, Rockford, 111., assignor to Sundstrand Corporation, a corporation of Illinois Filed Aug. 9, 1965, Ser. No. 478,247 4 Claims. (Cl. 91-198) This invention relates generally to hydraulic energy translating devices and more particularly to an axial piston hydraulic unit.

One type of axial piston hydraulic unit conventionally employs a rotary cylinder block with a plurality of axially disposed pistons reciprocable in the block. A relatively stationary valve member having inlet and outlet ports engages one end of the rotating cylinder block so that the cylinders in the block serially communicate with the inlet and outlet ports. In such devices the pistons may have spherical ends carrying pivotal slippers which engage an angular cam or swashplate member so that the pistons reciprocate in the cylinder block. When the hydraulic unit acts as a pump, fluid is drawn into the cylinders through the inlet port as the pistons withdraw therefrom. Piston return mechanisms are usually provided for withdrawing the pistons through the intake strokes and maintaining engagement between the slippers and the cam. After the pistons pass over bottom dead center they begin movement into the cylinders, discharging high pressure fluid through the outlet port in the valve member. When the device operates as a motor, the reverse operation occurs, with high pressure fluid entering the inlet port forcing the pistons out of the cylinders thereby effecting a rotation of the cylinder block.

In hydraulic units of the type described, a rotatable shaft is provided for driving the cylinder block when the device acts as a pump and for delivering output torque from the device when it acts as 'a motor. For this purpose the shaft must have a torque transmitting connection with the cylinder block. In the past this connection has taken the form of splines on the shaft directly engaging splines on the cylinder block. Further, in many of the prior devices, the splined portion of the drive shaft supports the cylinder block. It has been found desirable to provide not only some freedom of axal movement between the cylinder block and the shaft but also some limited freedom of misalignment between the shaft and the cylinder block. In order to properly locate the lateral support of the cylinder block in or near the plane of the centers of the piston spherical ends and also provide suflicient strength in the connection of the splines to the cylinder block, the length of the splines has been rather substantial, extending from within the cylinder block, outwardly throughout the length of a reduced cylinder block extension reaching the vicinity of the cam or swashplate. With splines of sufficient length, loose enough to allow cylinder block misalignment, high force couples are imposed on the cylinder block due to shaft deflection and cylinder block misalignment. In order to resduce the high couples, the splines on the shaft have been crowned, but this leads to point contact causing high stresses and excessive wear.

According to the present invention, the torque transmission between the cylinder block and the input or output shaft is effected by short splines which adequately transmit torque therebetween without imposing undesirable couples on the cylinder block even though there is some misalignment between the shaft and the block. The cylinder block is supported directly on the shaft in a manner to permit some freedom of misalignment, but separately from the splines. It has been found that when the block is supported on the shaft separate from the torque transmitting splines that the splines may be sub- 3,382,793 Patented May 14, 1968 stantially shorter than heretofore found necessary in the prior art devices, thus eliminating undesirable couples on the cylinder block.

It is, therefore, a primary object of the present invention to provide a new and improved axial piston hydraulic unit with means for supporting the cylinder block on the drive shaft and for transmitting torque therebetween without imposing undesirable couples on the cylinder block.

Another object of the present invention is to provide a new and improved axial piston hydraulic unit in which torque is transmitted between 'a rotary cylinder block and drive shaft by short splines and in which the cylinder block is supported on the drive shaft separately from the splines in a manner to permit freedom of misalignment between the shaft and the cylinder block.

A more specific object of the present invention is to provide a new and improved 'axial piston hydraulic unit including a housing member with a rotatable shaft mounted therein for transmitting torque to and from the unit; a cylinder block rotatable with the shaft and slidably receiving pistons with spherical ends pivotally interconnected with discrete slippers engaging a cam member for reciprocating the pistons with the cylinder block resiliently urged into engagement with the valve member by a spring biased against the shaft, with torque transmitted between the shaft and the cylinder block by a spherical retaining ball having two sets of short splines, one engaging splines on the shaft and the other engaging splines on the cylinder block, with the retaining ball resiliently biased toward the cam member into engagement with a piston retaining plate which holds the slippers against the cam member, the block being supported directly on a crowned portion of the shaft adjacent but separate from the shaft splines, this crown portion being generally aligned with a plane transverse to the cylinder block axis and passing through the intersection of a plane containing the piston pivotal interconnections and the axis of the cylinder block.

Other objects and advantages of the present invention will be readily apparent from the following detailed description taken in connection with the accompanying drawing which is a longitudinal cross section through an axial piston hydraulic unit incorporating the principles of the present invention.

While an illustrative embodiment of the invention is shown in the drawing and will be described in detail, herein, the invention is susceptible of embodiment in many different forms, and it should be understood that the present disclosure is to be considered as an exemplification of the principles of the invention and it is not intended to limit the invention to the embodiment illustr'ated. The scope of the invention will be pointed out in the appended claims.

Referring now to the drawing, an axial piston hydraulic unit is generally designated by the numeral 10. It should be understood that the unit 15) may be employed as either a pump or a motor, and includes a generally cylindrical housing member 11 which has a centrally disposed bore 12 for receiving and mounting the outer race of a roller bearing 13. A hollow shaft 15 is provided for delivering torque to or from the hydraulic unit depending upon whether the unit is operating as a pump or a motor. Shaft 15 is rotatably mounted at one end in the inner race of bearing 13.

A generally annular end cap 20 encloses the right end of bore 12 and is affixed by suitable means to the housing 11. End cap 20 receives a generally cylindrical stationary seal member 21 which has an annular sealing projection 22 slidably engaging the inner race of bearing 13. Shaft 15 is axially located by a shoulder 24 thereon which engages the inner bearing race 13. A resilient sealing ring 26 may be provided between the end cap and the stationary seal member 21.

The other end of the housing member 11 is enclosed by a generally cylindrical valve plate 27 fixed to the housing member by suitable fasteners (not shown). The valve plate 27 has conventional arcuate inlet and outlet ports formed therein opening to valve plate face 28. The arcuate ports communicate respectively with passages 29 and 30 which in turn communicate with threaded bores or ports 32 and 33 adapted to receive suitable hydraulic fittings.

A centrally disposed bore 36 extends axially from the valve plate face 28 in the valve member 27 and receives a suitable roller bearing 37 which rotatably supports the left end of the shaft 15. A shoulder 38 assists in locating shaft 15 axially.

A cylinder block 40 is rotatable with shaft 15 and has a flat end face 41 slidably engaging face 28 on valve member 27. A plurality of axial cylinders 43 are formed in the cylinder block 40 in annular array therein and each cylinder has a passage 45 therein for providing communication of the cylinders with the forward face of the cylinder block. Pistons 47 are slidably mounted in the cylinders 43 and have spherical ends 49. In order to reciprocate the pistons 47 in the cylinder block as the block rotates, a fixed angle cam member 51 is mounted in the housing 11. While cam member 51 is illustrated as being of the fixed displacement type, it should be understood that a variable angle Wobbler or swashplate could be used as well without departing from the primary principles of this invention. Driving connection between the cam member 51 and the pistons 47 is provided by individual slippers 55 having spherical sockets 56 therein which receive the spherical projections 49 on the pistons. The rear sides of slippers 55 slidably engage cam face 57 on cam member 51. Thus the slippers 55 and the spherical projections 49 define pivotal interconnecting means between the cam member 51 and the pistons 47 which permit universal movement therebetween.

A piston return mechanism is provided for maintaining the slippers 55 against the cam face 57 to assure the proper return of the pistons 47. For this purpose a spherical retainer member 6t: is provided which is axially slidable a limited distance with respect to cylinder block 40 and the shaft 15. A plurality of return springs 61 mounted in the cylinder block 40 engage an annular flange 64 on the spherical retainer which continuously urges the retainer 60 toward cam member 51. The spherical retainer 60 engages a retainer plate 66 having suitable openings 67 therein which receive the flange slippers 55. In this manner the retainer plate 66 holds the slippers 55 in engagement with cam surface 57 under the influence of return springs 61.

For the purpose of transmitting torque between the cylinder block 40 and the drive shaft 15, relatively short splines 70 are provided on shaft 15. Splines 70 interengage shorter internal splines 72 formed on the inside of the small end of the spherical retainer 60. The spherical retainer 60 has a second set of short internal splines 74 which engage complementary splines 75 formed on the outside of an annular cylinder block projection 77. In this manner torque may be transmitted in either direction between the cylinder block 40 and the shaft 15 through the spherical retainer 60. Splines 70, 72, 74 and 75 are short enough so that any misalignment between the shaft 15 and the cylinder block 40 will not produce any tilting moment on the cylinder block, whether this misalignment is due to the deflection of shaft 15 under load or an inherent manufacturing misalignment.

The cylinder block 40 is mounted on and supported laterally by the shaft 15. For this purpose shaft 15 has a longitudinally crowned portion 79 somewhat exaggerated in the drawing for the purpose of illustration. The crest -81 of crown 79 lies in a plane perpendicular to the axis of shaft 15 passing through the intersection (indicated at 85) of the axis of the shaft 15 and a plane (indicated at 87); containing the piston pivotal connections. Crowned portion 79 engages bore 90 formed within the cylinder block and extending through projection 77 thereof. The supporting crown portion 79 of shaft 15 is crowned so that there is some freedom of misalignment between the shaft 15 and the cylinder block 40 without producing undesirable tilting moments on the block. The crowned portion 79 is located or aligned about point 85 so that it most effectively resists any tilting moment on the cylinder block 40 caused by the cam member 51 acting through pistons 47.

As noted above, the utilization of a separate support for the cylinder block on shaft 15, such as crowned portion 79 and bore 90, permits the use of short torque transmitting splines which impose no tilting moment on the cylinder block. This results in a substantial increase in performance of the hydraulic unit 10 and a reduction in wear in the torque transmitting elements.

The cylinder block 40 is held against the valve member surface 28 by a compression spring 94 seated against a snap ring 95 on shaft 15 and biased against a bushing 96 engaging a snap ring 97 mounted in the cylinder block bore 99. The return springs 61 also assist in urging the cylinder block against the valve surface 28, but springs 61 may be arranged otherwise, as by grounding against the shaft 15.

When the hydraulic unit 10 operates as a pump, shaft 15 is connected to a suitable source of power and rotates the cylinder block 40 through the retainer member 60. Fluid then is drawn in through the inlet passage in the valve plate 27 into the cylinders and compressed therein as pistons 47 move into the cylinders under the influence of cam 51. The compressed fluid is discharged through the outlet port passage in valve plate 27. When the hydraulic unit is operated as a motor, high pressure fluid is delivered to the cylinders through the inlet passage in valve plate 27, effecting outward movement of the pistons from the cylinders thereby causing the cylinder block 40 to rotate driving the shaft 15, then an output shaft, through the spherical retainer 60.

I claim:

1. An axial piston hydraulic unit, comprising: a housing, valve means in said housing including an inlet port and an outlet port, a shaft rotatably supported in said housing, a cylinder block rotatable with said shaft and having one end thereof slidably engaging said valve means, said cylinder block having a plurality of axial cylinders therein, resilient means for biasing said cylinder block into engagement with said valve means, pistons slidable in said cylinder and having spherical ends projecting therefrom, a cam member adjacent said spherical ends adapted to reciprocate said pistons, slippers receiving said piston ends and connected to be driven by the cam member, said spherical ends and slippers defining pivotal connections, a generally spherical retaining member surrounding said shaft, a retaining plate engaging said spherical member and engaging said slippers, resilient means engaging said spherical member for urging the slippers toward said cam member, said cylinder block and spherical member having interengaging drive means, said spherical member and shaft having interengaging drive means, and means separate from said drive means for supporting said cylinder block on said shaft and permitting limited misalignment therebetween.

2. An axial piston hydraulic unit as defined in claim 1, wherein said cylinder block supporting means includes a crowned portion on said shaft engaging said cylinder block, said crowned portion being generally aligned with a transverse plane extending through the intersection of a plane containing the piston pivotal connections and the axis of the cylinder block.

3. An axial piston hydraulic unit as defined in claim 2. and further including an axial annular projection on said cylinder block, said spherical member surrounding said annular projection, said cylinder block and spherical member interengaging means including splines on said projection and on the adjacent interior of the spherical memher, said shaft and spherical member interengaging means including splines on said shaft spaced axially from said projection and splines on the adjacent interior of said spherical member, said shaft crowned portion engaging the interior of said cylinder block projection.

4. An axial piston hydraulic unit, comprising: a valve member having inlet and outlet ports therein, a rotatably mounted torque transmitting shaft, a cylinder block rotatable with said shaft and engaging said valve member, said cylinder block having a plurality of axially disposed cylinders therein, pistons slidable in said cylinders, a cam member adjacent one end of said cylinder block adapted to reciprocate said pistons, said pistons having pivotal connections with said cam member, a portion of said shaft being constructed to support said cylinder block thereon, said portion being located in a transverse plane extending through the intersection of a plane containing the piston pivotal connections and the axis of the cylinder block, spline means on said shaft separate from said portion for transmitting torque between the shaft and the cylinder block, said supporting shaft portion being defined by a crowned portion integral with said shaft and having a References Cited UNITED STATES PATENTS 3,187,644 6/1965 Ricketts 9257 3,228,303 1/1966 Budzich 91-198 3,232,056 2/1966 Heinrich et a1 91199 3,249,061 5/ 1966 Ricketts 103-162 FOREIGN PATENTS 831,673 3/1960 Great Britain.

MARTIN P. SCHWADRON, Primary Examiner.

PAUL E. MASLOUSKY, Examiner. 

1. AN AXIAL PISTON HYDRAULIC UNIT, COMPRISING: A HOUSING, VALVE MEANS IN SAID HOUSING INCLUDING AN INLET PORT AND AN OUTLET PORT, A SHAFT ROTATABLY SUPPORTED IN SAID HOUSING, A CYLINDER BLOCK ROTATABLE WITH SAID SHAFT AND HAVING ONE END THEREOF SLIDABLY ENGAGING SAID VALVE MEANS, SAID CYLINDER BLOCK HAVING A PLURALITY OF AXIAL CYLINDERS THEREIN, RESILIENT MEANS FOR BIASING SAID CYLINDER BLOCK INTO ENGAGEMENT WITH SAID VALVE MEANS, PISTONS SLIDABLE IN SAID CYLINDER AND HAVING SPHERICAL ENDS PROJECTING THEREFROM, A CAM MEMBER ADJACENT SAID SPHERICAL ENDS ADAPTED TO RECIPROCATE SAID PISTONS, SLIPPERS RECEIVING SAID PISTON ENDS AND CONNECTED TO BE DRIVEN BY THE CAM MEMBER, SAID SPHERICAL ENDS AND SLIPPERS DEFINING PIVOTAL CONNECTIONS, A GENERALLY SPHERICAL RETAINING MEMBER SURROUNDING SAID SHAFT, A RETAINING PLATE ENGAGING SAID SPHERICAL MEMBER AND ENGAGING SAID SLIPPERS, RESILIENT MEANS ENGAGING SAID SPHERICAL MEMBER FOR URGING THE SLIPPERS TOWARD SAID CAM MEMBER, SAID CYLINDER BLOCK AND SPHERICAL MEMBER HAVING INTERENGAGING DRIVE MEANS, SAID SPHERICAL MEMBER AND SHAFT HAVING INTERENGAGING DRIVE MEANS, AND MEANS SEPARATE FROM SAID DRIVE MEANS FOR SUPPORTING SAID CYLINDER BLOCK ON SAID SHAFT AND PERMITTING LIMITED MISALIGNMENT THEREBETWEEN. 